An antenna is provided, including: a first substrate, having has a first and a second surfaces parallel to each other and having a dielectric; a second substrate, having a third and a fourth surfaces parallel to each other, the third surface being disposed to face and abut the second surface, having a dielectric; a first radiation conductor, formed on the first surface; a second radiation conductor, formed on the third surface; and a power supply, supplying power to the first and second radiation conductors. A position of the power supply is disposed from centers of the first and second radiation conductors by distance d. A distance between a position where a reflection loss with respect to the second high-frequency signal becomes the smallest and the centers is d0, d/d0 is equal to or larger than 4/3.